The TV mogul has been allocated the over-25s in a public vote, while Cheryl Fernandez-Versini, who had the girls last year, will be mentoring the groups. New judge Rita Ora has been given the girls, with Nick Grimshaw taking charge of the boys.

The vote was decided by fans of the ITV show in one of the latest twists for the 12th series.

Cowell, who also mentored "the overs" in last year's series and steered winner Ben Haenow and runner-up Fleur East to the final, tweeted: " Wasn't the category I was expecting. I did win last year with the Overs so I'm sure we will do great things this year."

He previously wrote: " I mentored the overs last year and had the winner and the runner up. Great singers in this category, but I would be keen to see how another judge would do with the overs this year!"

The 55-year-old previously revealed his intention to coach the girls or the groups, tweeting: "It would be great to mentor the groups, as you saw tonight, there are some amazing ones this year! Vote for #SimonGroups," adding: "I do have the best track record with the groups after all...none of the others can do a better job."

He also wrote: "I would love to mentor the girls this year. The girls category needs an expert and that's me! Vote for #SimonGirls

"@Cherylofficial had them last year but I've not mentored the girls since Leona, and look what happened! #SimonGirls. Love the boys category but I had three guys in my Overs last year, it would be more fun to mentor something different."

The judges' categories were revealed on the X Factor Twitter account.

"*Drum roll please* We can reveal that @RitaOra will be mentoring... The Girls! #XFactor," read one post.

"You decided @SimonCowell should mentor... The Overs! #XFactor . @CherylOfficial will be mentoring The Groups...and @grimmers has The Boys! #XFactor"

The X Factor, which see Olly Murs and Caroline Flack taking over hosting duties from Dermot O'Leary, returned to ITV last weekend.

Some of the acts who impressed the judges to get through to the next round include Filipino girl group 4th Power, 21-year-old car mechanic Josh Daniel, 25-year-old dental receptionist Lauren Murray, and 17-year-old Essex student Louisa Johnson.